Effect of physicochemical parameters on the polygalacturonase of an Aspergillus sojae mutant using wheat bran, an agro-industrial waste, via solid-state fermentation

BACKGROUND: Polygalacturonases (PGs) are valuable enzymes of the food industry; therefore it is of great importance to discover new and GRAS PG-producing microbial strains. In this study, PG enzyme produced from a high PG activity producer mutant Aspergillus sojae using wheat bran at the flask scale under pre-optimized conditions of solid-state fermentation (SSF) was biochemically characterized. RESULTS: The crude PG enzyme showed optimum activity in the pH range 4.0-5.0 and was stable in the pH range 3.0-7.0. The optimum temperature for the PG was 40 degrees C and it retained 99% of its activity at 50 degrees C. The mutant A. sojae PG could preserve more than 50% of its stability between 25 and 50 degrees C, both for 30 and 60 min, and was found to be stable in the presence of most of the tested compounds and metal ions. The inactivation energy (E-d) was determined as 125.3 kJ mol(-1). The enthalpy (Delta H*), free energy (Delta G*) and entropy (Delta S*) of inactivation were found to be stable with increasing temperature. CONCLUSION: The mutant A. sojae PG could be suitable for the clarification (depectinization) of orange and grape juices and wine. (C) 2015 Society of Chemical Industry